Earthquakes

A whole lot of shake’n going on!

Earthquake terms:

• EARTHQUAKE-Vibration of the Earth caused by the rapid release of energy in the crust.

• Motion takes place along a FAULT.• Energy radiates out from the FOCUS.• Energy moving outward from the focus travels

in the form of SEISMIC WAVES.• The EPICENTER is the point above the focus on

the surface of the Earth.

http://www.digitalgeology.net/page1.html

What causes the rock to break?

• STRESS- Forces that push and pull on the Earth’s crust.

• Three types of stress:– Compression – Tension– Shear

As rocks undergo stress they can:

–Change shape–Change volume–Move up–Move down–Move sideways– Fracture or breakThis is called

deformation

Types of faults:

• Normal– Stress-tension

• Reverse– Stress-compression

• Strike slip– Stress-shear

http://www.iris.edu/gifs/animations/faults.htm

• http://video.nationalgeographic.com/video/player/environment/environment-natural-disasters/earthquakes/earthquake-montage.html

Types of Seismic Waves

• P-Wave: longitudinal wave. Travels 6 m/s. Passes through solids, liquids, and gases.

• S-Wave: transverse wave. Travels 3.5 m/s. Passes through solids.

• Surface Wave: Travels along the surface. Most destructive.

• http://www-rohan.sdsu.edu/~rmellors/lab8/l8maineq.htm#swave

Putting it all together

How a seismograph works

• http://www.wwnorton.com/college/geo/egeo/flash/8_3.swf

Reading P and S waves